Runtime command pinned out! Re-organized coolant pins.

- Pinned out cycle start(A2), feed hold(A1), and reset(A0) runtime
commands. These pins are held high with the internal pull-up resistor
enabled. All you have to do is connect a normally-open switch to the
pin and ground. That's it.

- Moved the coolant control pins to A3 (and the optional mist control
to A4).

- Moved all of the MASK defines into the config.h file to centralize
them.

stepper.h

@@ -25,15 +25,9 @@
 #include <avr/io.h>
 
 // Some useful constants
-#define STEP_MASK ((1<<X_STEP_BIT)|(1<<Y_STEP_BIT)|(1<<Z_STEP_BIT)) // All step bits
-#define DIRECTION_MASK ((1<<X_DIRECTION_BIT)|(1<<Y_DIRECTION_BIT)|(1<<Z_DIRECTION_BIT)) // All direction bits
-#define STEPPING_MASK (STEP_MASK | DIRECTION_MASK) // All stepping-related bits (step/direction)
-#define STEPPERS_DISABLE_MASK (1<<STEPPERS_DISABLE_BIT)
-
 #define TICKS_PER_MICROSECOND (F_CPU/1000000)
 #define CYCLES_PER_ACCELERATION_TICK ((TICKS_PER_MICROSECOND*1000000)/ACCELERATION_TICKS_PER_SECOND)
 
-
 // Initialize and setup the stepper motor subsystem
 void st_init();